This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To test hypothesis that the interaction of decidual macrophages with extravillous trophoblasts can be mediated through interaction of the non-classical MHC class I molecule Mamu-AG, expressed on rhesus trophoblasts, with leukocyte immunoglobulin-like receptors, expressed on macrophages. Leukocyte Ig-like receptors (LILRs) are a family of receptors that have inhibitory and activating functions and widely expressed by lymphoid and myeloid cells. To identify the rhesus monkey LILRs we performed screening of rhesus spleen and decidua cDNA libraries and RT-PCR cloning. We obtained eight different full length clones with structural and functional diversity similar to human LILRs, including LILRs with immunoreceptor tyrosine-based inhibitory motifs, LILRs with truncated cytoplasmic tails containing positively charged arginine residues in the transmembrane domain, and putative soluble receptors lacking transmembrane or cytoplasmic domains. Phylogenetic tree analysis of rhesus, chimpanzee and human LILR genes reveals two distinct clusters and orthologous relationship between Mm-LILRAd and hLILRA3, and Mm-LILRBc and hLILRB4. Characterization of rhesus LILRs will facilitate use of this nonhuman primate model for the study of the functional role (s) of LILRs, including immune regulation through interaction with non-classical MHC class I molecules. This research used WNPRC Research Services. NIH/NICHD funding for this five-year project ended March 2008, just before this reporting period began. Publications are pending.